Low power navigation devices, systems and methods

ABSTRACT

A system and method are disclosed for conserving power during navigation, e.g., user device pointer/cursor navigation, using a fingerprint image sensor, that may comprise processing, via a computing device, fingerprint image sensor data indicative of finger position and movement with respect to a fingerprint image sensor surface in a finger navigation mode to determine if the finger is in a first finger navigation mode; processing, via the computing device, fingerprint image sensor data indicative of finger position and movement with respect to a fingerprint image sensor surface in a finger navigation mode to determine if the finger is in a second finger navigation mode; and transitioning, via the computing device, the fingerprint image sensor from a first power consumption mode to a second power consumption mode, based on detecting a transition from the first finger navigation mode to the second finger navigation mode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of copending U.S. patentapplication Ser. No. 14/956,033, filed Dec. 1, 2015, which is acontinuation of U.S. patent application Ser. No. 14/037,647, filed Sep.26, 2013 (issued as U.S. Pat. No. 9,208,371), which claims the benefitof U.S. Provisional Application No. 61/707,725, filed Sep. 28, 2012. Theaforementioned patent applications are incorporated herein by referencein their entireties.

FIELD

The present application relates to a method for power conservation foran electronic device, and, more particularly, to a method for conservingpower in a finger sensor of a fingerprint imaging apparatus during usageof the finger sensor for navigation.

BACKGROUND

Finger scanners have been developed that detect the motion of the fingerand translate the finger motion into corresponding motion (navigation)of a cursor or pointer. Such finger scanners have been integrated inlaptop computers, cell phones, personal digital assistants, and otherelectronic devices. Since many of these devices are portable, they arefrequently powered by batteries. In such devices, the conservation ofpower during the use of the finger scanner for navigational purposes isdesirable because this will extend the useful period of batteryoperation.

SUMMARY

It will be understood by those skilled in the art that a system andmethod for conserving power during navigation using a fingerprint imagesensor is disclosed which may comprise receiving at a computing devicefingerprint image sensor data indicative of finger position with respectto a fingerprint image sensor surface in a finger navigation mode todetermine if the finger is in a first finger navigation mode; processingvia the computing device, fingerprint image sensor data to determine thepresence of redundant fingerprint image data to detect the finger in asecond finger navigation mode; and transitioning via the computingdevice, the finger sensor from a first power consumption mode to asecond power consumption mode, based on detecting a transition from thefirst finger navigation mode to the second finger navigation mode. Thefirst navigation mode may be indicated by the finger being detected torelatively quickly be alternately in contact with and not in contactwith the finger sensor surface, and sensed fingerprint image data beingsubstantially non-redundant. The second finger navigation mode may bedetermined by the finger being detected to be in contact with the fingersensor surface and the sensed fingerprint image data being substantiallyredundant. The first finger navigation mode may comprise a scrollingfinger navigation mode; and the first power consumption mode maycomprise a high power mode selected when the finger is moving in contactwith the sensor surface and the second power consumption mode is a zeropower mode selected when the finger is not in contact with thefingerprint image sensor surface. The second finger navigation mode maycomprise a selection finger navigation mode; and the second powerconsumption mode may comprise an alternating low power mode and a highpower mode periodically selected to determine the continuing presence orthe absence of the redundancy in the sensed fingerprint image data.

It will be understood that a system and method are disclosed forconserving power during navigation, e.g., user device pointer/cursornavigation, using a fingerprint image sensor, that may compriseprocessing, via a computing device, fingerprint image sensor dataindicative of finger position and movement with respect to a fingerprintimage sensor surface in a finger navigation mode to determine if thefinger is in a first finger navigation mode; processing, via thecomputing device, fingerprint image sensor data indicative of fingerposition and movement with respect to a fingerprint image sensor surfacein a finger navigation mode to determine if the finger is in a secondfinger navigation mode; and transitioning, via the computing device, thefingerprint image sensor from a first power consumption mode to a secondpower consumption mode, based on detecting a transition from the firstfinger navigation mode to the second finger navigation mode.

The system and method may also comprise, wherein the first navigationmode is indicated by the finger being detected to relatively quickly bealternately in contact with and not in contact with the finger sensorsurface. The system and method may also comprise, wherein the firstnavigation mode is indicated by the sensed fingerprint image data beingsubstantially non-redundant. The system and method may also comprise thefirst navigation mode being indicated by the finger being detected torelatively quickly be alternately in contact with and not in contactwith the finger sensor surface and the sensed fingerprint image databeing substantially non-redundant.

The system and method may also comprise, wherein the second navigationmode is indicated by the finger being detected to be relatively steadilyin contact with the finger sensor surface. The system and method mayalso comprise, wherein the second navigation mode is indicated by thesensed fingerprint image data being substantially redundant. The systemand method may also comprise the first navigation mode being indicatedby the finger being detected to be relatively steadily contact with thefinger sensor surface and the sensed fingerprint image data beingsubstantially redundant.

The system and method may also comprise periodically energizing, via thecomputing device, the fingerprint image sensor, during a period of timethe fingerprint image sensor is determined to be in the first navigationmode, to detect a transition of the finger position from a firstposition relative to the fingerprint image sensor surface to a secondposition relative to the fingerprint image sensor surface; anddetermining, via the computing device, that fingerprint image sensordata received from the energized fingerprint image sensor is indicativeof lateral motion of a finger being sensed in relation to thefingerprint image sensor surface. The system and method may alsocomprise periodically energizing, via the computing device, thefingerprint image sensor, during the a period of time the fingerprintimage sensor is determined to be in the second navigation mode, todetect fingerprint image sensor data indicative of no lateral motion ofa finger being sensed in relation to the fingerprint image sensorsurface.

The system and method may also comprise a non-transitory computerreadable medium storing instructions that, when executed by a computingdevice, cause the computing device to perform a method for conservingpower during navigation using a fingerprint image sensor, the methodwhich may comprise processing, via a computing device, fingerprint imagesensor data indicative of finger position and movement with respect to afingerprint image sensor surface in a finger navigation mode todetermine if the finger is in a first finger navigation mode;processing, via the computing device, fingerprint image sensor dataindicative of finger position and movement with respect to a fingerprintimage sensor surface in a finger navigation mode to determine if thefinger is in a second finger navigation mode; and transitioning, via thecomputing device, the fingerprint image sensor from a first powerconsumption mode to a second power consumption mode, based on detectinga transition from the first finger navigation mode to the second fingernavigation mode.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.References include, for example, U.S. Pat. No. 7,099,496 B2 to Benkley,issued Aug. 29, 2006, for Swiped Aperture Capacitive Fingerprint SensingSystems and Methods; U.S. Pat. No. 7,463,756 B2 to Benkley, issued Dec.9, 2009, for Finger Position Sensing Methods and Apparatus; U.S. Pat.No. 8,165,355 B2 to Benkley, issued Apr. 24, 2012, for Method andApparatus for Fingerprint Motion tracking Using an In-Line Array for Usein Navigation Applications; U.S. Pat. No. 7,751,601 B2 to Benkley,issued Jul. 6, 2010, for Finger Sensing Assemblies and Methods ofMaking; U.S. Pat. No. 8,229,184 B2 to Benkley, issued Jul. 24, 2012, forMethod and Algorithm for Accurate Finger Motion Tracking; U.S. Pat. No.7,643,950 B1 to Getzin, issued Jan. 5, 2010, for System and Method forMinimizing Power Consumption for an Object Sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 is a schematic drawing of a low power navigation finger sensorconstructed in accordance with one embodiment of the presentapplication;

FIG. 2 is a schematic drawing of a power conservation module of the lowpower finger sensor shown in FIG. 1;

FIG. 3 is an illustration showing a finger in fast motion on a surfaceof the low power finger senor shown in FIG. 1;

FIG. 4 is an illustration showing a finger in slow motion on the surfaceof the finger senor shown in FIG. 1; and

FIGS. 5a-d is a graph which depicts the position of a finger on thesurface of the low power finger sensor (5A), the voltage applied to thelow power finger sensor (5B), and the low power finger sensor wake-up onevent unit status (5C), and the lines scanned by the low power sensor(5D).

DETAILED DESCRIPTION

A method is provided which conserves power during the use of a fingersensor for navigational purposes. A computing device receives fingersensor data which is indicative of finger motion with respect to afinger sensor surface and processes the finger sensor data to determinethe presence of a first finger navigation mode or a second fingernavigation mode. It will be understood that the real finger motion canhave many different “modes” or characteristics of movement across thesensor. For purposes of the present disclosure, it can be presumed thatmost of the time the finger will be in one of the two modes discussedabove. Therefore, one can implement strategies that take advantage ofthis observation. When the finger moves in such a way that neither ofthese modes describes the motion, then the sensor can, for example,remain awake and consuming higher power or can be placed in low power,e.g., after some selected threshold time of such non-descript motionmode(s). It will be understood, however, that the two modes occur oftenenough that the average power will be dominated by the average powerconsumed according to the operation in each of these two modes asdescribed in the present application. The computing device transitionsthe finger sensor from a first power consumption mode to a second powerconsumption mode based on detecting a transition from the first fingernavigation mode to the second finger navigation mode. It will also beunderstood that the system does not actually or necessarily switch fromone mode to the other. The CPU can be looking for both motioncharacteristics simultaneously, and there may be periods, as justdiscussed, where the sensor is in neither of the modes described abovein this application.

Although the present application can be used in conjunction with anytype of finger sensor, it is particularly suitable for use in connectionwith a finger sensor adapted for finger navigation of a cursor orpointer. Accordingly, the present application will be describedhereinafter in connection with such a finger sensor. It should beunderstood, however, that the following description is only meant to beillustrative of the present application and is not meant to limit thescope of the present application, which has applicability to other typesof finger sensors, such as security fingerprint scanners.

The present application overcomes the shortcomings discussed above byproviding a low power finger scanner that conserves power during the useof the finger scanner for navigational purposes. A method for thevariation of the voltage level of a finger scanner, which is supportedby firmware code and digital logic, has a usage model that has fast andslow finger motion modes. As noted, the finger can have other modes ofmotion which are not relevant to system and method as disclosed in thisapplication in the sense that these other modes need not be exploitednor accounted for, as the system and method can take advantage of onlythe fast or slow motions described herein. For instance, during fingernavigation there are pauses in the contact of the finger with the sensorsurface during navigational motion of the finger, of which the user maynot even be aware. These pauses can be used, in both the fast and slowmotion modes, to turn the sensor off, when it is not needed, and to turnthe sensor back on when it is needed, thereby conserving power.

In the fast motion mode, during consistent large/rapid gestures (e.g.,in order to move the cursor rapidly towards a target icon or object orother position on the screen), the finger is only in contact with thesensor for brief intervals at a time, followed by what may even belarger intervals of time for lifting and repositioning the finger.During the intervals of time in which finger is lifted off of thesurface of the sensor, power to the sensor can be turned off, and whenthe finger is repositioned back onto the surface of the sensor, a fingerdetect circuit can detect when the finger has returned to the surface ofthe sensor and turns the power to the sensor back on.

In the slow motion mode, in which the finger is moving slowly with finetuning motions, for example in positioning a cursor onto or hoveringabove a target icon, the duration of such finger motions is much longerthan the sensor's scanning time intervals. During the intervals of timein which the sensor senses that finger motion scanned data is notchanging significantly, but the finger is still indicated to be on thesensor, the sensor can be put on a lower power mode, thereby conservingpower. Periodically, e.g., under the control of a wake on event unit,the sensor returns to full power and evaluates a few scan lines. If thefew scan lines that are evaluated during this time are stillsubstantially the same as the last unique line (i.e., the scan lines arestill redundant and the finger is still moving slowly or not moving atall), the sensor can be returned to the lower-power mode. However, ifthe sensor detects a unique scan line, the scanner can remain in fullpower and continues scanning lines.

FIGS. 1 and 2 illustrate a low power finger sensor 10 is constructed inaccordance with one embodiment of the present application. The low powerfinger sensor 10 includes a finger sensor 12 and a power conservationmodule 14. It is understood that the finger sensor 12 can include aconventional finger sensor such as the relative motion sensor disclosedin U.S. Pat. No. 8,165,355 B2 to Benkley, et al., entitled Method andApparatus for Fingerprint Motion Tracking Using an In-Line Array for Usein Navigation Applications, which is incorporated by reference herein inits entirety. The low power finger sensor 10 has a sensor surface 16, acentral processing unit (CPU) 18 which is powered by a CPU power supply20, and a wake-up on event (WOE) unit 22 which is powered by a WOE unitpower supply 24.

As shown in FIG. 2, the power conservation module 14 has a powerconservation CPU 26, a power conservation logic unit 28 and a powercontrol unit 30. The power conservation logic unit 28 receives andprocesses finger on/off surface signals 32 received from the fingersensor 12 and directs the power control unit 30 to send finger sensorCPU power control signals 34 and WOE unit power control signals 36 tothe CPU power supply 20 and the WOE unit power supply 24, respectively,for purposes described in the present application. The powerconservation logic unit 28 also receives and processes finger sensorscanned line signals 38, and directs the power control unit 30 to sendfinger sensor CPU power control signals 34 to the CPU power supply 20and the WOE unit power supply 24, respectively, for purposes describedin the present application. Alternatively, the system and method of thedisclosed subject matter could do without the Power conservation module14. In such an embodiment, the CPU 18 can hand off control to the WOEmodule 22, which can then also return control to the CPU 18. The WOEpower supply 24 never needs to actually turn off.

Accordingly, in such an embodiment, the CPU 18 can be collecting imagedata when the finger comes off the sensor 12. The CPU 18 can detect thisand stop scanning data, and may also hand control over to a statemachine in the WOE unit 22. The WOE state machine (not shown), can thenassume control, and can, e.g., kill power to the CPU 18 (via the CPUPower Supply 20), and the WOE unit 22 can then begin polling for afinger.

The examples of pulses, as seen, by way of example in FIG. 5c , do notrepresent the WOE power supply 24 switching on and off, since that maynot be happening, but instead those pulses represent sampling windows inthe WOE unit 22. So, in such an embodiment, the WOE power supply 24 canalways be on, but most of the time there are other circuits, which arepowered down until samples are needed. When samples are needed, the WOEstate machine can power up the sampling circuits, look for a finger, andthen power down the sampling circuits and wait until the next sampleinterval. During this entire time, however, the WOE state machine can berunning and counting time. Now, supposing that a finger comes down onthe sensor again. Sometime later, the WOE state machine can power up thesampling circuits, these circuits can detect the finger, and the WOEunit 22 can power up the CPU 18 and pass control back to it. Then theCPU 18 can start collecting lines of data, e.g., fingerprint image data.

For the second mode of operation, the CPU 18 can, e.g., be collectinglines of data, e.g., fingerprint image data. While collecting theselines of data, the CPU 18 can be constantly processing them forredundancy (e.g., it will be understood that, as an example, wheneverthe CPU is up, it is doing this analysis). If the CPU 18 determines thatthe last N lines were redundant, then the CPU 18 can pass control backto the WOE state machine, and, as will be understood, can at this timecommand the WOE state machine to not shut the CPU 18 all the way down,but instead to only pause the CPU 18 (i.e., as an example, turn off oneor more CPU clocks—not shown) and only lower the CPU power supply 20 tosome lower (non-zero) value. After a programmed interval, the WOE unit22 can restore power from or to the power supply 20 and pass controlback to the CPU 18.

In summary, by way of example, both modes can work such that the CPU 18can direct the WOE unit 22 to shut down the CPU, e.g., by de-energizingthe CPU and/or the power supply to the CPU, until such time as the WOEunit 22 detects a finger. Similarly, the CPU 18 can direct the WOE unit22 to pause the CPU 18, e.g., by turning off one or more clocks of theCPU, and/or, e.g., placing the CPU power supply in a lower power mode,and to wake up the CPU, e.g., after some selected time, e.g., a fewmilliseconds. It is understood that one or more embodiments of thepresent application may be implemented with one or more computerreadable media, wherein each medium may be configured to include thereondata or computer executable instructions for manipulating elements ofthe low power finger sensor 10 such as the power control unit 30 of thepower conservation module 14, as described below. The computerexecutable instructions include data structures, objects, programs,routines, or other program modules that may be accessed by a processingsystem, such as one associated with a general-purpose computer orprocessor capable of performing various different functions or oneassociated with a special-purpose computer capable of performing alimited number of functions. Computer executable instructions cause theprocessing system to perform a particular function or group of functionsand are examples of program code means for implementing steps formethods disclosed herein. Furthermore, a particular sequence of theexecutable instructions provides an example of corresponding acts thatmay be used to implement such steps. Examples of computer readable mediainclude random-access memory (“RAM”), read-only memory (“ROM”),programmable read-only memory (“PROM”), erasable programmable read-onlymemory (“EPROM”), electrically erasable programmable read-only memory(“EEPROM”), compact disk read-only memory (“CD-ROM”), or any otherdevice or component that is capable of providing data or executableinstructions that may be accessed by a processing system. Examples ofmass storage devices incorporating computer readable media include harddisk drives, magnetic disk drives, tape drives, optical disk drives, andsolid state memory chips, for example. The term processor as used hereinrefers to a number of processing devices including general purposecomputers, special purpose computers, application-specific integratedcircuit (ASIC), and digital/analog circuits with discrete components,and other computing devices, for example.

A. POWER CONSERVATION METHODS

In an embodiment, the low power finger sensor 10 has at least twomethods for conserving power during the use to scan a fingertip 40 of afinger 42 on the sensor surface 16 of the finger sensor 12, fornavigation of a cursor, pointer or similar icon towards a targetelement. The first method for the conservation of power during the useof the low power finger sensor 10, for relatively fast motion of thefingertip 40 for rapidly navigating the cursor, pointer or similar icontowards a target element or position, is described in the presentapplication.

B. FAST FINGER MOTIONS

Referring to FIG. 3, the fingertip 40 of the finger 42 is depicted asquickly swiping on the sensor surface 16, then lifting, then swiping,then lifting, etc. The path of the swiping motion of the fingertip 40 isindicated by a curved arrow F. More particularly, the solid depiction ofthe fingertip 40 is shown contacting the sensor surface 16, and thephantom depiction of the fingertip 40 is shown not contacting the sensorsurface 16.

The power conservation logic unit 28 monitors the finger on/off surfacesignals 32, e.g., as depicted in the left hand side of FIG. 5a ,received from the finger sensor 12 and when it determines that thefingertip 40 is off of the sensor surface 16, it directs the powercontrol unit 30 to send a finger sensor power control signal 34 to theCPU power supply 20 to turn the normal voltage Vreg (e.g., Vreg=1.2volts) that powers the CPU 18 to off (i.e., Vreg is turned off, Vreg=0volts). That is, the voltage to the CPU will be 0 V when the finger isdetected to be “Off” the sensor, as depicted in the left hand side ofFIGS. 5a and 5b . Coincidentally, the power control unit 30 also sends aWOE unit power control signal 36 to the WOE unit power supply 24directing it to turn the voltage to the WOE unit 22 on, periodically,thereby turning the WOE unit 22 on periodically, as depicted in FIG. 5cwhile the finger is detected as “Off” the sensor (FIG. 5a ). When the“event” is the fingertip 40 being detected as coming back into contactwith the sensor surface 16 (for example, as shown in FIG. 5a ), the CPU18 operating at Vreg, e.g., 1.2V is turned back on, hence overall powerconsumption is reduced. The WOE unit 22 being periodically turned to“On” looks for the fingertip 40 to be on the sensor surface 16 (as,e.g., shown in the FIG. 5c “WOE unit status” graph). When the fingertip40 is determined to be on the sensor surface 16, the WOE unit 22 sends aWOE unit power control signal 36 to the power control unit 30, to directit to send a finger sensor CPU power control signal 34 to the CPU powersupply 20 to restore the CPU 18 voltage to Vreg, e.g., 1.2 V as depictedin FIGS. 5b and 5c , whereby regular scanning begins, as indicated bythe collection of scan lines as depicted in FIG. 5d while the CPU isturned “On” because the finger is detected as on the sensor surface 16and moving with respect to the sensor surface 16.

More particularly, referring to the left hand side of FIGS. 5a -5 d, thefingertip 40 of the finger 42 is picking, swiping and moving rapidly onthe sensor surface 16. While the fingertip 40 is on the sensor surface16 (as seen in FIG. 5a ), the CPU power supply 20 voltage is Vreg (asseen in FIG. 5b ) and the finger sensor 12 is scanning lines of data (asseen in FIG. 5d ), and the finger sensor 12 is consuming maximum power.When the fingertip 40 leaves the sensor surface 16, the powerconservation logic unit 28 detects this by monitoring the finger on/offsurface signals 32 (seen in FIG. 5a ), and it directs the power controlunit 30 to send a finger sensor CPU power signal 34 to instruct the CPUpower supply 20 to reduce the Vreg voltage to zero (seen in FIG. 5b )and thereby stop scanning data (see FIG. 5d ). Coincidentally the powercontrol unit 30 also directs the WOE unit power supply 24 toperiodically power on the WOE unit 22 (or alternatively to remain onthroughout the so-called “wait” mode), but only periodically connect tothe sensor to see if the finger remains “Off” the sensor, therebyconserving power while the fast moving fingertip 40 is off of the sensorsurface 16. This can be understood to be the state illustrated in FIG.5c with the WOE unit being “On” periodically, e.g., when the voltage tothe CPU 18 is “Off,” i.e., 0V. This process can be repeated over andover again until the power conservation logic unit 28 of the powerconservation module 14 determines that the fingertip 40 is movingslowly. It will be understood that in some embodiments there could beintermediate modes besides intermittently moving fast and more steadilymoving slowly. When the fingertip 40 is determined to be on the sensorsurface 16, but moving slowly, then a second method for the conservationof power may be utilized, as described below.

C. SLOW OR FINE TUNING FINGER MOTIONS

Referring to FIG. 4, the fingertip 40 of the finger 42 is depicted asmoving more slowly over the sensor surface 16. The path of the motion ofthe fingertip 40 is generally indicated by a straight arrow S. The soliddepiction of the fingertip 40 is shown contacting the sensor surface 16at a beginning position, and the phantom depiction of the fingertip 40is shown contacting the sensor surface 16 at an ending position. Moreparticularly, when the fingertip 40 slows down during its movement onthe sensor surface 16, for example, during fine tuning motions of thecursor when the cursor is closely approaching a target or position, thefingertip 40 moves slowly across the sensor surface 16, and manyconsecutive scan lines from the finger sensor 12 are redundant orsubstantially redundant. More particularity, referring to the FIG. 5c“WOE unit status” graph, the unique scanned lines are symbolized assolid black vertical lines, and the redundant scanned lines (vis-à-visone or more precedingly detected scan lines) are symbolized as dashedblack vertical lines. When enough consecutive scanned lines areredundant, which indicates that the fingertip 40 has not moved by asignificant amount, as indicated in the middle of FIG. 5d , the CPU 18of the finger sensor 12 can, e.g., be put into a lower power mode at avoltage Vlow (e.g., Vlow=0.6V instead of 1.2V) for a selectable andprogrammable amount of time, as indicated in FIG. 5b . Periodically thepower conservation logic unit 28 can return the CPU 18 power supply toVreg (as seen in FIG. 5b ) such that the system and method reviews a fewscan lines which it receives from the finger sensor 12 via a fingersensor scanned lines signal 38. If the few scanned lines are stillsubstantially the same as the last unique line (i.e., still redundant),as indicated in the right hand portion of FIG. 5d , then Vlow, e.g.,0.6V, is maintained, thereby conserving power. When a unique line isdetected, as indicated by the grouping on the far right of FIG. 5d , thepower conservation logic unit 28 directs the CPU power supply 20 toapply Vreg to the CPU 18 (as seen in FIG. 5c ), whereby regular scanningbegins, and, necessarily, the finger is being detected to be “On” thesensor surface 16 (as seen in FIG. 5a ).

More specifically, referring to the middle and right half of FIG. 5, asthe finger motion slows down, the WOE unit 22 is not in operation (asseen in FIG. 5c ) because the fingertip 40 remains touching the sensorsurface 16 (as seen in FIG. 5a ). As lines of data are scanned, some ofthem are unique (i.e., see for example, black lines as depicted on FIG.5d ) and some of them look mostly the same as the line(s) before them(as seen, for example, in the dashed black lines depicted on the rightof FIG. 5d ) because the finger has not moved by a significant amount.When enough successive redundant lines are seen, the power conservationlogic unit 28 detects this, stops the scanning of data, and puts thefinger sensor 12 into “WOE Retain” mode (right middle side of FIG. 5),wherein the CPU power supply 20 Vreg 1.20 volts is brought down to Vlow0.6 volts and the CPU 18 clock is disabled so the CPU 18 can't performany operations. Vlow is too low to operate the CPU 18 (i.e., clockingthe CPU 18 is not allowed), but it is still high enough that the CPU 18preserves all of it states. The fact that the CPU 18 is not operatingreduces the power consumed by the finger sensor 12, and the fact thatthe voltage is lowered reduces the leakage current in the finger sensor12, which also conserves power. After a programmable interval of time,the WOE state machine can, e.g., power up the CPU 18 and start theclocking of the CPU 18 again at Vreg, i.e., 1.2V as seen on the left ofFIG. 5b . The CPU 18 will collect some more scan lines of data and thepower conservation logic unit 28 will compare them with the last uniqueline that was detected. If the power conservation logic unit 28determines that the lines of data are still too similar to the lastunique line, and that the finger is moving so slowly that new fingerscan line data is not required to be collected for a while, the CPU 18be will be directed not to scan for a period of time. After a period oftime the power conservation logic unit 28 can again collect some morescan lines of data and compare them with the last unique line that wasdetected. When the power conservation logic unit 28 detects unique linesof fingerprint image data, and the CPU 18 can be directed to stay awakeand to continue to collect data. At the far right side of FIG. 5, thefinger 42 leaves the sensor surface 16, after which and the processesdescribed hereinabove can be repeated again upon the application fingernavigational motions on the sensor surface 16 of the low power fingersensor 10.

It will be understood that in one embodiment, finger motion, per se, atleast finger speed and finger movement direction, per se, need not bedetermined or known. The system and method may, e.g., detect and knowthat the finger is either on or off the sensor surface 16 (i.e., viasignal 32 in FIG. 2) and the data being collected is either redundant orunique, as determined using signal 38 in FIG. 2. Based on thosecharacteristics the system and method can then select the differentpower modes, including power savings modes. As an example, detection ofthe finger on or off the sensor can take precedence. For example, if thefinger is off the sensor and the last data, e.g., fingerprint imagedata, was redundant, then the WOE state machine can be in a mode ofwaiting for the finger to return (the periodic “On” times of FIG. 5c ),not the WOE retain mode (the periodic changes from Vreg to Vlow in FIG.5b ). However, if the finger is on the sensor surface 16, then thesystem and method may be in the “retain” mode reducing the voltage tothe CPU 18 to Vlow and periodically increasing to Vreg to check forcontinuing redundancy in the scanned lines. It will be understood thatthe time periods during which the CPU 18 is returned to Vreg arerelatively short and the scanning of a few lines can occur so fast that,even with a finger that is moving, but doing so slightly, can still keepthe CPU power supply at Vlow (while scan line redundancy continues forsome meaningful time) sufficiently to significantly reduce overall powerconsumption, and thus, increase overall battery life.

It will also be understood by those skilled in the art that a system andmethod is disclosed for conserving power during navigation using afingerprint image sensor, which may comprise receiving at a computingdevice fingerprint image sensor data indicative of finger position withrespect to a fingerprint image sensor surface in a finger navigationmode to determine if the finger is in a first finger navigation mode;processing via the computing device, fingerprint image sensor data todetermine the presence of redundant fingerprint image data to detect thefinger in a second finger navigation mode; and transitioning via thecomputing device, the finger sensor from a first power consumption modeto a second power consumption mode, based on detecting a transition fromthe first finger navigation mode to the second finger navigation mode.

The system and method may further comprise the first navigation modebeing indicated by the finger being detected to relatively quickly bealternately in contact with and not in contact with the finger sensorsurface, and sensed fingerprint image data being substantiallynon-redundant. That is to say, as will be understood by those skilled inthe art, that the “scrolling” finger navigation mode may be detected bythe occurrence of rapid changes of detection of the finger from “On” to“Off” and back to “On” the sensor surface, as is typical for suchscrolling motions by a person using the device of the disclosed subjectmatter, which may be determined, e.g., from empirical data for astatistically significant portion of the population or even learned overtime for a given user of the device, or both. Statistically significantvariation from such a selected or determined range and/or number ofsuccessive “Ons” and “Offs” can also be used to determine that the useris not in or has discontinued the described “finger scrolling”navigational mode.

This system and method of the disclosed subject matter may comprise thesecond finger navigation mode being determined by the finger beingdetected to be in contact with the fingerprint image sensor surface andthe sensed fingerprint image data being substantially redundant. It willbe understood by those skilled in the art that substantially redundantdoes not require complete redundancy over any selected time period andthat any redundancy at all need not switch the fingerprint image sensorfrom regular operation to “selection” navigation mode. That is to say,even in regular fingerprint image selection operating mode, occasionallydue to such phenomena as a relatively slow swipe of the finger acrossthe sensor surface and/or the effects of restriction, some redundancy isexpected and normally handled by the fingerprint image reconstructionoperation of a fingerprint imager of the type discussed in the presentapplication. The substantial redundancy referenced in the disclosedsubject matter refers to a persistent redundancy, e.g., for a period oftime indicative of the fact the fingerprint image sensing system andmethod will not produce a reconstructed fingerprint image in areasonable period of time, e.g., several seconds, and/or a reasonablenumber of total detected image scans from the fingerprint image sensor,e.g., within some multiple, e.g., 1-2 of a time or a number of scansthat are ordinarily required to capture the required multiple images toreconstruct a single fingerprint image. These time periods or scannumbers or the like, useful in defining “substantially” in the contextof such fingerprint image sensor systems and methods as discussed in thepresent application, if not already well known to those in the art, and,therefore not necessary of specific disclosure in the presentapplication, are, at a minimum, discoverable without undueexperimentation, and devices clear to anyone skilled in the art, aspertains to claim interpretation.

The system and method may further comprise the first finger navigationmode comprising a scrolling finger navigation mode and the first powerconsumption mode comprising a high power mode, e.g., a normal full poweroperating voltage, selected when the finger is moving in contact withthe sensor surface and the second power consumption mode may be a zero,or substantially zero, power mode, e.g., a normal “Off” mode for thesystem or any respective component, selected when the finger is not incontact with the fingerprint image sensor surface.

The system and method may further comprise the second finger navigationmode comprising a selection finger navigation mode and the second powerconsumption mode may comprise an alternating low power mode (e.g.,somewhere intermediate the normal operating voltage and zero voltagethat, e.g., allows for the component being so powered to carry out somesubset of its usual operations, but not all, i.e., is conserving powereven at that intermediate voltage, and a high power (normal orsubstantially normal operating voltage) mode periodically selected todetermine the continuing presence or the absence of the redundancy inthe sensed fingerprint image data. As an example, as noted above, theintermediate “low power” voltage could allow a CPU to maintain all ofits internal states, but not operate as a CPU, e.g., not be clocked.

It will be understood that a system and method are disclosed forconserving power during navigation, e.g., user device pointer/cursornavigation, using a fingerprint image sensor, that may compriseprocessing, via a computing device, fingerprint image sensor dataindicative of finger position and movement with respect to a fingerprintimage sensor surface in a finger navigation mode to determine if thefinger is in a first finger navigation mode; processing, via thecomputing device, fingerprint image sensor data indicative of fingerposition and movement with respect to a fingerprint image sensor surfacein a finger navigation mode to determine if the finger is in a secondfinger navigation mode; and transitioning, via the computing device, thefingerprint image sensor from a first power consumption mode to a secondpower consumption mode, based on detecting a transition from the firstfinger navigation mode to the second finger navigation mode.

The system and method may also comprise, wherein the first navigationmode is indicated by the finger being detected to relatively quickly bealternately in contact with and not in contact with the finger sensorsurface. The system and method may also comprise, wherein the firstnavigation mode is indicated by the sensed fingerprint image data beingsubstantially non-redundant. The system and method may also comprise thefirst navigation mode being indicated by the finger being detected torelatively quickly be alternately in contact with and not in contactwith the finger sensor surface and the sensed fingerprint image databeing substantially non-redundant.

The system and method may also comprise, wherein the second navigationmode is indicated by the finger being detected to be relatively steadilyin contact with the finger sensor surface. The system and method mayalso comprise, wherein the second navigation mode is indicated by thesensed fingerprint image data being substantially redundant. The systemand method may also comprise the first navigation mode being indicatedby the finger being detected to be relatively steadily contact with thefinger sensor surface and the sensed fingerprint image data beingsubstantially redundant.

The system and method may also comprise periodically energizing, via thecomputing device, the fingerprint image sensor, during a period of timethe fingerprint image sensor is determined to be in the first navigationmode, to detect a transition of the finger position from a firstposition relative to the fingerprint image sensor surface to a secondposition relative to the fingerprint image sensor surface; anddetermining, via the computing device, that fingerprint image sensordata received from the energized fingerprint image sensor is indicativeof lateral motion of a finger being sensed in relation to thefingerprint image sensor surface. The system and method may alsocomprise periodically energizing, via the computing device, thefingerprint image sensor, during the a period of time the fingerprintimage sensor is determined to be in the second navigation mode, todetect fingerprint image sensor data indicative of no lateral motion ofa finger being sensed in relation to the fingerprint image sensorsurface.

The system and method may also comprise a non-transitory computerreadable medium storing instructions that, when executed by a computingdevice, cause the computing device to perform a method for conservingpower during navigation using a fingerprint image sensor, the methodwhich may comprise processing, via a computing device, fingerprint imagesensor data indicative of finger position and movement with respect to afingerprint image sensor surface in a finger navigation mode todetermine if the finger is in a first finger navigation mode;processing, via the computing device, fingerprint image sensor dataindicative of finger position and movement with respect to a fingerprintimage sensor surface in a finger navigation mode to determine if thefinger is in a second finger navigation mode; and transitioning, via thecomputing device, the fingerprint image sensor from a first powerconsumption mode to a second power consumption mode, based on detectinga transition from the first finger navigation mode to the second fingernavigation mode.

It will be understood that the embodiments described herein are merelyexemplary and that a person skilled in the art may make many variationsand modifications without departing from the spirit and scope of theapplication. All such variations and modifications are intended to beincluded within the scope of the application as defined in the appendedclaims. As an example, the finger scanner can be a linear or twodimensional swiped scanner array. In addition, the rapid finger motionon and off the surfaces as described with respect to FIG. 3 could beinvoking a scrolling navigational movement. In addition, the slowerfinger motion staying in contact with the sensor surface could alsoutilize finger speed as measured using the scan data, or otherwise.Also, a fast mode of operation like that described for FIG. 3 could beemployed as the finger is sensed to be moving faster across the surface(e.g., above some threshold speed) moving rapidly towards a target orposition and a slow mode, like that described for FIG. 4 when the fingeris sensed to be more slowly moving (below some threshold speed) as thecursor or the like gets closer to the target or position and is focusingin on the particular target or position or hovering over such position.Also, the low power mode can be involved when the finger is removed fromthe surface and hovers over the cursor or the like after navigating thecursor or the like to the target or position which thereafter remainsunmoving.

The invention claimed is:
 1. A system, comprising: a fingerprint imagesensor; and a computing device, configured to: monitor signals from thefingerprint image sensor; determine, based on the signals from thefingerprint image sensor, that a finger is not in contact with a sensorsurface of the fingerprint image sensor, and, in response thereto,operate the fingerprint image sensor in a wake-on-event mode; duringoperation of the fingerprint image sensor in the wake-on-event mode,periodically activate the fingerprint image sensor to determine whethera finger is in contact with the sensor surface; and in response todetermining that a finger is in contact with the sensor surface duringoperation of the fingerprint image sensor in the wake-on-event mode,transition the fingerprint image sensor into a higher power scanningmode to detect finger motion relative to the sensor surface and togenerate corresponding finger sensor data indicative of the detectedfinger motion, wherein the higher power scanning mode consumes higherpower relative to the wake-on-event mode.
 2. The system according toclaim 1, wherein the computing device is further configured toalternately operate the fingerprint sensor in the wake-on-event mode andthe higher power scanning mode during a first finger navigation mode,wherein the first finger navigation mode corresponds to a fingeralternately in contact with and not in contact with the sensor surface.3. The system according to claim 1, wherein the computing device isfurther configured to operate the fingerprint image sensor in a secondfinger navigation mode, wherein the second finger navigation modecorresponds to a finger motion where a finger is maintained in contactwith the sensor surface.
 4. The system according to claim 1, wherein thecomputing device is configured to reduce power consumption for aninterval in response to determining that data collected by thefingerprint image sensor is redundant.
 5. The system according to claim1, wherein the computing device is configured to reduce powerconsumption in the wake-on-event mode relative to the higher powerscanning mode by turning off one or more clocks of a processor and/or byplacing a power supply of the processor into a lower power mode.
 6. Amethod of operating a fingerprint image sensor to conserve power, themethod comprising: monitoring, by a computing device, signals from thefingerprint image sensor; determining, by the computing device, based onthe signals from the fingerprint image sensor, that a finger is not incontact with a sensor surface of the fingerprint image sensor, and, inresponse thereto, operating the fingerprint image sensor in awake-on-event mode; during operation of the fingerprint image sensor inthe wake-on-event mode, periodically activating, by the computingdevice, the fingerprint image sensor to determine whether a finger is incontact with the sensor surface; and in response to determining that afinger is in contact with the sensor surface during operation of thefingerprint image sensor in the wake-on-event mode, transitioning, bythe computing device, the fingerprint image sensor into a higher powerscanning mode to detect finger motion relative to the sensor surface andto generate corresponding finger sensor data indicative of the detectedfinger motion, wherein the higher power scanning mode consumes higherpower relative to the wake-on-event mode.
 7. The method of claim 6,further comprising: alternately operating the fingerprint image sensorin the wake-on-event mode and the higher power scanning mode during afirst finger navigation mode, wherein the first finger navigation modecorresponds to a finger alternately in contact with and not in contactwith the sensor surface.
 8. The method of claim 6, further comprising:operating the fingerprint image sensor in a second finger navigationmode, wherein the second finger navigation mode corresponds to a fingermotion where a finger is maintained in contact with the sensor surface.9. The method of claim 6, further comprising: reducing power consumptionfor an interval in response to determining that data collected by thefingerprint image sensor is redundant.
 10. The method of claim 6,further comprising: reducing power consumption in the wake-on-event moderelative to the higher power scanning mode by turning off one or moreclocks of a processor and/or by placing a power supply of the processorinto a lower power mode.
 11. A non-transitory computer-readable mediumhaving processor-executable instructions stored thereon for conservingpower using a fingerprint image sensor, wherein the processor-executableinstructions, when executed by a computing device, facilitateperformance of the following: monitoring signals from the fingerprintimage sensor; determining, based on the signals from the fingerprintimage sensor, that a finger is not in contact with a sensor surface ofthe fingerprint image sensor, and, in response thereto, operating thefingerprint image sensor in a wake-on-event mode; during operation ofthe fingerprint image sensor in the wake-on-event mode, periodicallyactivating the fingerprint image sensor to determine whether a finger isin contact with the sensor surface; and in response to determining thata finger is in contact with the sensor surface during operation of thefingerprint image sensor in the wake-on-event mode, transitioning thefingerprint image sensor into a higher power scanning mode to detectfinger motion relative to the sensor surface and to generatecorresponding finger sensor data indicative of the detected fingermotion, wherein the higher power scanning mode consumes higher powerrelative to the wake-on-event mode.
 12. The non-transitorycomputer-readable medium of claim 11, wherein the processor-executableinstructions, when executed, further facilitate: alternately operatingthe fingerprint image sensor in the wake-on-event mode and the higherpower scanning mode during a first finger navigation mode, wherein thefirst finger navigation mode corresponds to a finger alternately incontact with and not in contact with the sensor surface.
 13. Thenon-transitory computer-readable medium of claim 11, wherein theprocessor-executable instructions, when executed, further facilitate:operating the fingerprint image sensor in a second finger navigationmode, wherein the second finger navigation mode corresponds to a fingermotion where a finger is maintained in contact with the sensor surface.14. The non-transitory computer-readable medium of claim 11, wherein theprocessor-executable instructions, when executed, further facilitate:reducing power consumption for an interval in response to determiningthat data collected by the fingerprint image sensor is redundant. 15.The non-transitory computer-readable medium of claim 11, wherein theprocessor-executable instructions, when executed, further facilitate:reducing power consumption in the wake-on-event mode relative to thehigher power scanning mode by turning off one or more clocks of aprocessor and/or by placing a power supply of the processor into a lowerpower mode.